When trying to add between 200 and 600 members to a private list, in batches, I’m receiving many errors. Sometimes it works, but more often than not, it will return over capacity, page not found, or something more obscure like “error 757: unexpected token at ‘’”. I’ve tried adjusting the batch size from 100 down to about 10, and that doesn’t seem to make too much difference - once a list starts throwing errors, it seems to keep doing so. Backing off doesn’t help - even a day later some lists are still throwing the same errors.

I’m using the ruby twitter gem, and this method should correspond to lists/members/create_all. My understanding is that this API call isn’t rate limited, and the numbers I’m trying to add should be well within the user limits. It doesn’t seem to make a difference whether I specify the members by screen name or id. Is there something I’m missing about how this is supposed to work?